1. Field of the Invention
The present invention relates to a treatment liquid supply system that supplies treatment liquid used for coating industrial objects for film formation including a semiconductor substrate, a display substrate, a glass and the like, and in particular, to a treatment liquid supply system that performs supply control of a small flow amount of the treatment liquid by using a nozzle that vacuum-sucks and injects the treatment liquid from a treatment liquid tank.
2. Description of the Related Art
There is an earlier treatment liquid supply system where, when a film is coated on a semiconductor substrate and a display substrate in a manufacturing process of a semiconductor apparatus, a liquid crystal display apparatus and so on, as shown in FIG. 7, a wafer 1 rotates at a high speed with the wafer 1 being supported horizontally and treatment liquid 3 is dripped at a location near a central bore 2 of the wafer 1 from above the wafer 1.
Centrifugal force effecting on the treatment liquid 3 dripped on the wafer 1 that rotates at a high speed makes the treatment liquid to radially spread out on the surface of the wafer 1 to form a film as coated on the entire surface of the wafer 1.
As another example, in case where treatment liquid is coated on a semiconductor substrate and a display substrate by spray coating, as shown in FIG. 8, a treatment liquid supply system that comprises a treatment liquid tank 6 storing treatment liquid 5 therein, a treatment liquid supply pipe 7 connected to the treatment liquid tank 6, and a nozzle 8 connected to the treatment liquid supply pipe 7 wherein the nozzle 8 discharges the treatment liquid 5 supplied from the treatment liquid tank 6. A flow amount adjustment valve 9 such as a needle valve is disposed in the middle of the treatment liquid supply pipe 7 to control supply amount of the treatment liquid to the nozzle 8 whereby the treatment liquid 5 is discharged for coating from the nozzle 8 by controlling a flow amount of the treatment liquid supply through the flow amount adjustment valve 9 with the treatment liquid 5 inside the treatment liquid tank 6 being pressurized or with the treatment liquid 5 being supplied by a pump (not shown).
In the earlier apparatus as shown in FIG. 7, however, when an amount of the treatment liquid 3 dripped on the wafer 1 becomes so small, the treatment liquid 3 does not disperse well. Therefore, the treatment liquid 3 of more than 10 ml/min is necessary to drip for film formation on the entire surface of the wafer1. As a result, the treatment liquid 3 disperses toward the outer direction by centrifugal force of the high-speed-rotating wafer1 and part of the treatment liquid 3 is coated on the surface of the wafer 1 and the rest thereof drops outside of the wafer 1.
As described above, an efficiency of the treatment liquid coating deteriorates and the treatment liquid supply apparatus is not economical due to a large amount of the treatment liquid 3 being dripped, as well as being wasted discarded outside of the wafer 1. Moreover, An environment around the apparatus is possibly polluted by the treatment liquid 3 wasted outside of the wafer1.
In the earlier apparatus as shown in FIG. 8, flow control of the treatment liquid 5 supplied to the nozzle 8 is performed by the flow amount adjustment valve 9 such as a needle valve disposed in the middle of the treatment liquid supply pipe 7 and as a result, such flow amount adjustment valve 9 does not enable flow control of the treatment liquid 5 at an amount of 1 ml/min or less than it. Therefore, it is difficult to evenly coat a film on an object by supplying the treatment liquid 5 of less than 1 ml/min. Further, if foreign matter such as dusts and carbons is mixed with the treatment liquid 5 inside the treatment liquid tank 6, it causes plugging in the flow amount adjustment valve 9 disposed in the treatment liquid supply pipe 7 to the nozzle 8, thereby to block supplying of the treatment liquid 5 to the nozzle 8 and therefore, processing of a treatment liquid coating does not proceed smoothly.